A resin liner for a safe with a steel outer shell takes advantage of desirable characteristics of both materials. A resin liner makes the safe's interior versatile and moisture resistant, and a steel outer shell adds strength and durability. U.S. Pat. Nos. 4,048,926 and 3,408,966 have recognized the possibility of such a combination; and more recently, the assignee of this application has manufactured steel shell safes with resin liners. The steel shells were formed without back panels, and the resin liners were inserted from the rear to seat against the inside of front frames of the steel shells. The rear steel panels were then assembled to the backs of the safes, and insulation was poured into spaces between the resin liners and the steel outer shells.
All these suggestions have left room for improvement. For example, assembling a back panel to a steel shell after a liner is in place involved interconnections between the back panel and the liner and proved to be more expensive than welding the back panel to the shell as the rest of the shell is fabricated. Also, problems have persisted with insulation material leaking from a junction between the liner and the steel shell. The present invention aims to solve these problems and reduce assembly cost while taking advantage of the properties of a steel outer shell and a resin liner for a fire-resistant safe.